1. Field of the Invention
The present invention relates to a method applied to the manufacturing process of a fluid injection device, and particularly to a method of manufacturing a fluid injection device with precise fluid chambers and flow channels by applying a step of etching compensation or an ion implantation step.
2. Description of the Related Art
Presently, fluid injection techniques are widely applied in a multitude of potential applications, such as the liquid droplet injector of inkjet printers, fuel injection systems, drug delivery systems and bioengineering systems. In recent years, semiconductor manufacturing process has generally been applied to fabricate small fluid injection devices with reliability and low cost. Since silicon wafers are commonly used in the semiconductor manufacturing process, such as IC, opt-electronics, microelectronics or MEMS, it is preferable to use the silicon wafer as the substrate for the fluid injection device.
An example of the conventional fluid injection device can be described with reference to FIG. 1. FIG. 1 shows a fluid injection device 10 with a virtual valve, such as a microinjector, disclosed in U.S. Pat. No. 6,102,530. The fluid injection device 10 constitutes a silicon substrate 38, which has a manifold 26 to supply the fluid, a plurality of fluid chambers 14 at a side of the manifold 26 containing the fluid, a plurality of orifices 18 connected to the corresponding fluid chamber 14 to eject the fluid, and a plurality of injection components 20, 22 near the orifices 18.
However, silicon wafers are anisotropic. That is, anisotropic etching occurs along each direction of the lattice of the silicon substrate when etching. This phenomenon can be detailed with reference to FIGS. 2a and 2b. 
FIG. 2a is an example of the silicon wafer 500. A corrosion-resisting hard mask layer 510 is provided on the lattice plane {100} of the silicon wafer 500. The hard mask layer 510 is provided with an opening, so that the silicon substrate 520 is etched with an etching fluid (not shown), such as the potassium hydroxide (KOH) solution. In the etching process, the etching rate along each direction of the lattice of the silicon substrate 520 differs, in which etching along the [110] direction has a higher rate. Thus, inclined planes 522, 524 on the lattice plane {111} with a relative angle xcex8=54.74xc2x0 to the lattice plane {100} are obtained on the silicon substrate 520.
FIG. 2b is another example of the silicon wafer 500, in which the opening on the hard mask layer 510 in FIG. 2b has a different shape than the opening in FIG. 2a. In this case, an inclined plane 526 on the lattice plane {111} and an inclined plane 528 on the lattice plane {112} are obtained.
Consequently, in the anisotropic etching process for manufacturing the manifold 26 and the fluid chambers 14 of the conventional fluid injection device 10 as shown in FIG. 3a, since the etching rate varies along each direction of the lattice of the silicon substrate 38 in the anisotropic etching process, overshoot (that is, over etching) occurs in a certain portion of the substrate 38 that forms the isolating beams 30 to separate the fluid chambers 14. Thus, the actual size of the fluid chambers 14 manufactured can differ from the desired size in design. In this case, crosstalk between the adjacent fluid chambers 14 may occur, particularly when the fluid chambers 14 are placed in arrays with close pitch.
Further, if the overshoot significantly occurs in the end portions of the isolating beams 30, a plurality of etching tips 31 is formed in these end portions, which further leads to stress concentration. In this case, the strength of the isolating beams 30 is weakened, and the operation lifetime of the fluid injection device 10 is shortened. This stress concentration effect is magnified if the fluid injection device 10 has a relatively small size.
In view of this, an object of the present invention is to rearrange the manufacturing process of the fluid injection device, so that the fluid injection device can be manufactured in a small and precise structure with relatively reduced crosstalk or overshoot from the anisotropic etching process.
The present invention discloses a method of manufacturing a fluid injection device. The fluid injection device has a plurality of fluid chambers and a plurality of isolating portions separating the fluid chambers, in which the isolating portions are formed with a predetermined geometric shape.
The method of manufacturing the fluid injection device may include the steps of: providing a substrate; providing a mask with a compensating pattern thereon; coating a photoresist layer on the substrate; deploying the compensating pattern onto the photoresist layer to determine a plurality of unetched isolating portions, wherein the unetched isolating portions are formed with a compensated geometric shape larger than the predetermined geometric shape; and etching the substrate to form the isolating portions with the predetermined geometric shape.
In the above-mentioned method, deployment comprises steps of: performing exposure on the photoresist layer with the mask; and performing development on the photoresist layer to form the unetched isolating portions on the photoresist layer. The compensated geometric shape can be a shape formed by increasing a certain area to the predetermined geometric shape of the isolating portions along at least one direction of the lattice of the substrate.
Further, the method of manufacturing the fluid injection device may include the steps of: providing a substrate; performing ion implanting on a predetermined area on the substrate for the isolating portions; and etching the substrate to form the isolating portions with the predetermined geometric shape.
In the above-mentioned method, the ion used for implantation can be boron, phosphorous, or arsenic.
Further, the method of manufacturing the fluid injection device may include the steps of: providing a substrate; providing a mask with a pattern thereon; coating a photoresist layer on the substrate; deploying the pattern onto the photoresist layer to determine a plurality of isolating geometries, wherein the isolating geometries are formed larger than the predetermined geometric shape; and etching the substrate to form the isolating portions with the predetermined geometric shape, wherein the isolating portions comprise at least one extrusion to prevent the adjacent fluid chambers from crosstalk in ejecting the fluid.
In the above-mentioned method, the deploying step is described in the following detailed steps of: performing exposure on the photoresist layer with the mask; and performing development on the photoresist layer to form the isolating geometries on the photoresist layer.
The fluid injection device applied in the method of the present invention may have a fluid storage tank storing the fluid, a manifold connecting the fluid storage tank and the fluid chambers for guiding the fluid from the fluid storage tank in the fluid chambers, a plurality of heating devices respectively disposed in the fluid chambers for heating the fluid in the corresponding fluid chamber, a plate structure supporting the heating devices, and a plurality of injection orifices respectively connected in the fluid chambers for ejecting the fluid in the corresponding fluid chamber therethrough.
Further, in the above-mentioned methods of the present invention, the substrate can be a monocrystalline material or an anisotropic material, and the etching step can be applied with a wet etching process.